This invention relates to microscopes used in Fourier Transform infrared (FTIR) spectrometer systems. The disclosed microscope is intended to be part of a modular system, in which the function of microscopic analysis is only one of several (or many) options readily available to the operator.
Industrial and forensic chemists have been turning increasingly to infrared microscopy as a problem-solving adjunct to Fourier-transform infrared (FTIR) spectroscopy. The combined technique uses a microscope attachment to an FTIR spectrophotometer to get transmission or reflectance spectra of regions or particles less than 10 micrometers in diameter. One reason for the rising popularity of the method is that detailed chemical information can be obtained from very small samples or highly localized regions. Another reason is the recent availability of low-cost, benchtop FTIR spectrophotometers with optics good enough for the purpose.
Microscopes of this type in themselves have multiple uses. They permit microscopic observation in the visual range, and also permit infrared analysis of the sample, using the modulated output beam of an interferometer spectrometer. The visual mode is also used to move the sample into place for use of the IR analytical beam. Additionally, the IR beam may be designed to analyze the sample in either the transmission mode or the reflectance mode.
Providing an effective reflectance mode has been a major challenge for the suppliers of FTIR microscopes, because of the very low radiation throughput obtained in the reflectance mode of most FTIR microscopes. This problem is effectively dealt with in a copending application assigned to the assignee of the present application application Ser. No. 907,995, filed Sept. 16, 1986.
In general, FTIR microscopes have not been designed in such a way as to fit into a versatile FTIR spectrometer system. In fact, truly versatile systems of this type have only recently been developed, as disclosed in two other copending, common assignee applications application Ser. No. 895,211, filed Aug. 11, 1986; and application Ser. No. 900,730, filed Aug. 27, 1986. Those applications relate, respectively, to ensuring maximum radiation throughput in a multi-unit spectrometer system, and to providing modular "building blocks" which permit cost-effective and functionally efficient assembling and re-assembling of such multi-unit spectrometer systems.